The present invention relates to an expandable reinforcing member or stent suitable for a vessel with a branch.
"Stent", which is defined here as a prosthetic member used for reinforcing the blood vessel, has been used in the interluminal vascular treatment in place of surgical exposing, incising, removing, replacing or bypassing a defected portion of a blood vessel required in the conventional vascular surgery.
The stent generally has a tubular shape and functions to support a part of a blood vessel or other anatomical lumen from the inside thereof, and is particularly suitable for supporting and holding a dissected arterial lining which may occlude a fluid passageway by collapse thereof.
There are many types of stents, such as tubular stent formed of a tubular metal plate with holes therein by cutting or etching, wire stent formed of a flat or round wire and arranged in a cylindrical shape, self expanding stent, and balloon expanding stent, and so on.
In view of the reason that the stent is placed in a patient's body cavity, i.e. blood vessel, to support a cavity wall, generally speaking, the tubular stent with the holes therein is better than the wire stent, because the tubular stent can withstand a high radial force to support the cavity wall. However, since a wire stent can be relatively easily moved and/or deformed after installation in the blood vessel, it is convenient to use the wire stent for the blood vessel with a branch. Namely, if a wire segment of the wire stent blocks a branch hole of a blood vessel when the wire stent is installed by a balloon catheter, the wire stent can be slightly moved further by the balloon catheter not to block the hole of the branch.
In this respect, since the outer surfaces of the tubular stent is not so smooth, after the stent is expanded and installed in the blood vessel, it is difficult to move the stent. Also, it is difficult to dispose the tubular stent without blocking the branch hole. Thus, it is better not to use the conventional tubular stent when the blood vessel with the branch portion is to be supported.
On the other hand, when the stent is installed into the blood vessel, the stent in a closed condition is mounted on a catheter, e.g. balloon catheter, and delivered to the lesion or stenosis by the balloon catheter. Since the stent in the closed condition is not flexible in the longitudinal direction thereof, if the stent is long, it is difficult to deliver the stent through a meandering artery in and around the calcified lesion without damaging the blood vessel.
In this respect, if the diameter of the stent in the closed condition is small, it is easy to pass the narrow and meandering artery. However, the small diameter stent can not be expanded too large, because when the stent is expanded widely, the stent can not sufficiently support. Namely, in order to sufficiently support the artery, the stent must have a large number of supports, so that the stent can not be expanded to have a large diameter. Otherwise, the stent must have a large diameter.
Accordingly, one object of the invention is to provide a stent, which provides a support on a main vessel and a large opening for a side branch.
Another object of the invention is to provide a stent as stated above, wherein the stent can be slightly moved and/or deformed easily after installation if required.
A further object of the invention is to provide a stent as stated above, which can be easily delivered through the meandering and narrow artery without damaging the vessel.
Further objects and advantages of the invention will be apparent from the following description of the invention.